Hello,

Is it possible to share a single host's Logical Volume among multiple local KVM guests which mount it read-only?

I'm asking this because I have an idea to run multiple idential KVM guests (they all have exactly the same software installed on them), booting them from a shared local Logical Volume read-only root file system, or alternatively let them share the bulk of the software (/usr, /opt, /lib) from a common KVM host Logical volume.

Is this possible? All my searches so far failed to turn up anything like this.

Would it be possible using qcow2 instead of raw LV? If so - would it be worth the performance hit of switching from LV to qcow2?

The motivation for this is two-fold:
1. Speed-up - I suspect that sharing the same disk block among all KVM agents (we currently have 14 KVM guests on each server) should lead to better cache utilisation and reduce disk access. Also the cost of maintaining the mutiple identical servers and keeping them up to date could be eating into our server's resource usage.
2. Maintenance - if I get to share the common disk image among all of them then I only need to install/update it once instead of once for each KVM guest (we already use Puppet but it doesn't mean it comes for free).

Thanks,

--Amos